Free Astronomy Magazine September-October 2014

ASTROBIOLOGY what uncertain, to say the least. Lin and colleagues have therefore adopted a low-pro- file strategy, which will none- theless allow to verify their hypothesis. Primarily, the three researchers made a list of pol- lutants that in the Earth’s at- mosphere show a significant absorption (dark lines) in the spectral range covered by JWST. The easiest to detect among the CFCs were tetra- fluoromethane (CF 4 ) and tri- chlorofluoromethane (CCl 3 F), both unquestionably produ- ced by human activity. The first of the two has a maxi- mum absorption right in the middle of the infrared at 7.8 µ m (micron), and is strongly masked by the absorption of CH 4 and N 2 O; while the second, instead, leaves a more noticeable trace at 11.8 µ m, near which are this time O 3 and H 2 O to cause the heaviest interference. Supposing wanting to identify CF 4 and CCl 3 F in the at- mosphere of an Earth-like planet located at a reasonable distance (say within a few hundred light-years from Earth), in order to succeed with JWST their abundances will have to be about 10 times higher than those currently measurable in our atmo- sphere. In this case the total integration time (sum of all exposure times) necessary to record the absorption lines of the two CFCs would respectively be of 1.7 and 1.2 days, which are reasonably close to those (about 1.0 day) necessary to record the pres- ence of classical biomarkers (traces of which must be duly sub- tracted to highlight those of the CFCs, where they overlap). The search for CF 4 and CCl 3 F would not therefore weigh sig- nificantly on what will be the programs of study of extraso- lar planets that as- tronomers will start with JWST. In actual fact it will be possi- ble to kill the pro- verbial two birds with one stone: not only it will be possi- ble to understand whether there is life on a certain planet, E ven around white dwarfs can planets form, as confirmed by some debris disks discovered in the vicinity of some of them. Above we can see an artist’s represen- tation of one of those disks, while on the left, in the field of the Hya- des star cluster, are shown two white dwarfs as- sociated with de- bris disks [Jon Lomberg, NASA, ESA, STScI, and Z. Levay (STScI)]